The Ladette: If Becky and Nikki's rivalry over Bart is any like the rivalry between Ryoko and Ayeka in Tenchi Muyo!, then Nikki best fits this role, except she isn't your tradition version of this trope.

Psycho Ex-Girlfriend: While Bart did share a brief love interest with her, she ultimately descends from hot and cold flirt into this after training with Mr. Burns, and declares a showdown against Becky. After Nikki's defeat, this is toned down quite a bit.